Copper or rust color on an a body

1971dodgedart/6 said
WOW! i love that color! if you ever happen to get the code thats awsome!

from my fender tag its, KT5, which doesn't seem to be recognize by online fender tag decoder.
From a Plymouth 1974 paint chart they have T5, which is Sienna Poly. Wondering what the K in front mean